tools/jxlinfo: improve CLI option parsing (#1383)
tools/jxlinfo: improve CLI option parsing (#1383)

* tools/jxlinfo: improve CLI option parsing

This patch adds --help, --verbose, and other convenience
features, such as the ability to read multiple files with
jxlinfo.
libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl